The present invention relates to a gripping strip for disposable syringes having a syringe cylinder with an end on which the gripping strip is fixedly mounted as a separate synthetic plastic part.
In this construction the gripping strip has a plate-shaped abutment with a hollow cylindrical receptacle whose outer diameter is smaller than the inner diameter of the syringe cylinder, and in the region of the outer surface arresting elements are formed for a form-locking operative connection for mounting on the syringe cylinder. The syringe cylinder has an inner undercut which is complementary to the arresting elements. In the interior of the receptacle, a safety ring is inserted for maintaining the operative connection. Syringes for medical and diagnostic purposes have a gripping strip on the syringe cylinder which is formed as a counter support during pressing of the piston into the syringe cylinder for application process, whether its manual or by means of a injection pump.
This gripping strip is also identified as a finger support and a cylinder gripping plate. The connection of the gripping strip with the syringe cylinder must withstand pulling out forces, up to 100 N.
There are two basic concepts for arranging the gripping strip of the syringe cylinder. In accordance with the first concept, the gripping strip is formed of one piece with the syringe cylinder during its manufacture. Because of the geometry of the plate shaped abutment which deviates from the circular form, the gripping strip during filling interferes with the syringe, and it must have a relatively great distance between the magazine syringe bodies projecting during filling. In the case of glass syringes, a certain breakage damage and the danger of sliding of the finger during the application process exists, which was found by patients to be very unpleasant.
In accordance with a second concept from the which the present invention is derived, the gripping strip is formed as a separate synthetic plastic part and subsequently, or in other words after the filling process, is mounted on the syringe cylinder which can be composed of glass or synthetic plastic. With this concept the disadvantages of the first concept with the one-piece formed gripping strip can be eliminated.
Since the gripping strip must withstand high pulling out forces, the strength or stability of the connection of the synthetic plastic gripping strip with the syringe cylinder is especially important.
It is known to mount the syringe cylinder in the interior of the hollow cylindrical receptacle of the gripping strip. This type of mounting has a substantial disadvantage that the wall of the hollow cylindrical receptacle projects opposite to the diameter of the syringe cylinder with a sharp edge transition to the syringe cylinder. The required axial expansion of the receptacle takes over the outer surface of the syringe cylinder which is required for example, for the label. This axial extension interferes during the reception of the syringe in the injection pump, and with certain pump types prevents such a reception. On the other hand, in the known gripping strips, a relatively great synthetic plastic mass is needed for manufacture. This is on the one hand unfavorable for the disposal and on the other hand increases manufacturing costs, the features which are extremely important for disposable articles. In addition, the arrangement of the mounting of the gripping strip is relatively expensive.
In the above mentioned patent document DE 39 24 830 A1, the finger application on the syringe cylinder must be relatively simply arrestable with the use of a louver baffle cap, but such a connection withstands only low pulling out forces. As a rule, the synthetic plastic griping strip shrinks under the action of preliminary heating. This step requires substantial expenses during the manufacture, or in other words, an expensive mounting, to provide a very accurate temperature control. In addition, when the gripping strip is too cold, it can not be mounted, but when the temperature is too high, it can melt. The heating negatively influences the filling agent and also interferes with the filing in the cleaning chamber in which it is desired to obtain a flow from above downwardly, which is disturbed by the upwardly oriented heat flow.
The patent document WO 92 08507, FIG. 1 (equivalent to U.S. Pat. No. 5,364,369, FIG. 17) discloses a gripping strip for prefilled disposable syringes with the syringe cylinder, having an end with a gripping strip fixedly mounted on it as a separate synthetic plastic part. It has a plate-shaped abutment with a hollow cylindrical receptacle having an outer diameter which is smaller than the inner diameter of the syringe cylinder. An arresting element formed as a ring groove is provided in a socket-like manner on the outer surface of the hollow cylindrical receptacle, or a form-locking operative connection with the syringe cylinder which has a complementary inner edge bead.
In this known gripping strip, the receptacle is mounted in the interior of the syringe cylinder. Thereby the gripping strip does not occupy any surface of the outer casing of the syringe cylinder, there is no sharp edge transition between the gripping strip and the casing of the syringe cylinder which can cause an injury danger, and due to the geometry the syringe is insertable in injection pumps in a simple manner without any problems.
The principal disadvantage of this construction is however that the gripping strip can not withstand any high pulling out forces, since the form-locking arresting connection can be readily releasably released. The above mentioned WO 92 08507 document in FIG. 5 shows an alternative embodiment with an inner undercut on the syringe cylinder and a complimentary edge bead on the hollow cylindrical receptacle, with an additional outer arresting connection composed of a edge bead on the syringe cylinder and a claw-shaped formation on the plate-shaped abutment of the gripping strip. The pulling forces which it withstands in this embodiment are also low, since the form-locking connection can be easily broken. In addition, due to the deviation from the cylindrical shape on the base of the syringe cylinder, the insertion into the injection pumps causes certain problems.
The same is true for the above mentioned U.S. Pat. No. 5,364,369 which in FIG. 13 shows the gripping strip with the hollow cylindrical receptacle of separate peripheral portions and formed projections for an outer form-locking connection with an outer border edge formed on the edge of the syringe cylinder.
The German document DE 44 34 614 A1 discloses in FIG. 1C the above identified gripping strip which can withstand high pulling out forces. The reason is that the form-lock of the operative connection is maintained by the safety ring and is insertable in the injection pump without any problems, since a small cylinder surface is available up to the abutment of the gripping grip.
The known gripping strip requires relatively high manufacturing and mounting expenses. It must be produced with two separate parts, namely the plate-shaped abutment with the receptacle and the safety ring, and must have these parts on the device to be supplied to the manufacturing process. In addition, the material consumption is very high due to the massive design of the gripping strip part, that has the above mentioned negative consequences with respect to the disposability and manufacturing cost, which is exceptionally important in the manufacture of mass articles.